They are not as strong as the later 5 speeds I wouldn't go with one of the early trans. Yes they(the later G52-54 , W56 and R trannies) are longer but the work will be well worth it. You don't have to modify the crossmember but you do have to move it back. You have to relocate the mounts, with mine a set of ubolts were used to move the x-member. The d-shafts had to be shortened/lengthened but that's done pretty cheap.
Angelo told me my L52SHD was as strong as a W56
at one point i was thinking of putting the 22RTE i had in my truck and Angelo told me he was sure my L52SHD would hold up to it fine
